This invention relates to polyarylate polymers and, more particularly, to a method for forming a polyarylate polymer coating on a substrate and to an article that includes such a coating.
In a variety of applications of practical importance, the need exists for overlaying a substrate with a layer of material having prescribed characteristics. Sometimes this need can be adequately met by bonding or otherwise securing a sheet of the material to the substrate. But, for many commercially significant applications, this approach is not completely satisfactory. Often, a more conformal and adherent overlayer, such as can be provided only by an applied coating of the material, is required.
Polyarylate polymers constitute a known class of plastic materials having a number of advantageous characteristics such as excellent electrical, mechanical, thermal and flammability properties. The relative ease with which these materials can be injection molded or extruded has led to their use in a number of industrial applications.
One significant commercial use for polyarylate polymer materials is as a covering for surfaces in the reaction chamber of a plasma-assisted etching apparatus, as disclosed in a copending commonly assigned U.S. patent application of J. M. Moran designated Ser. No. 295,839, filed Aug. 24, 1981 now U.S. Pat. No. 4,397,724. Illustratively, at least some of the surfaces in the immediate vicinity of a workpiece to be etched in such a chamber are covered with a sheet of a polyarylate polymer. Typically, the sheet is secured by screwing, riveting or adhesive bonding to an underlying substrate in the chamber. Contamination of the workpiece during the etching process is thereby substantially reduced, as described in detail in the aforecited application.
In practice, use of a sheet of polyarylate polymer material affixed to a substrate in an etching chamber sometimes leads to buckling or warping of the polymer material. In addition, cracking of the material, perhaps caused by stresses introduced into the material during molding or extrusion, sometimes occurs. And, in many cases, it is difficult or impossible to affix a sheet of the polyarylate polymer in a reliably adherent and conformal way to curved or relatively inaccessible surfaces in the etching chamber.
In view of the above, efforts have been directed by workers in the art aimed at trying to coat layers of polyarylate polymers onto substrates. But, heretofore, no completely satisfactory procedure for applying a coating of such a polymer to a substrate has been specified. It was recognized that if such a procedure could be devised, it would enable the attainment of a polyarylate-polymer-coated substrate having enhanced characteristics such as improved adhesion, better conformity and low stress. Accordingly, the development of such a coating for use in etching chambers, as well as in a variety of other industrial processes, has been a much-sought-after goal.